(CNN) -- A new U.S. law aims to ensure that smart phones are not helping fund wars in Congo and neighboring countries.

The provision -- tucked in the financial reform bill passed this week -- requires publicly-traded and electronic companies such as Apple and Intel to submit an annual report outlining what they are doing to ensure their minerals are "conflict-free."

The Democratic Republic of Congo is rich in resources, including cobalt, gold, copper and tantalum.

Some U.S. companies buy minerals used in jewelry, computers and cell phones from the war-ravaged eastern part of the country, where government forces have been battling rebels for years. Rights groups say profits from the minerals help fund the militants.

The bill does not mention the penalty for using conflict minerals, but says companies will have to certify where their minerals come from and what measures were taken to ensure they did not originate from conflict areas.

Results and disclosures would then be posted on the companies' websites, according to the bill.

"This is a step in the right direction," said Frederick Golooba-Mutebi, a senior research fellow at Makerere University in neighboring Uganda, who regularly visits Congo. "It protects the interests of the Congolese ... a lot of minerals are going to be certified, and the law will do away with fly-by-night businesses and introduce bona fide companies that don't infringe on the rights of the the people."

However, he cautioned, there's still work to be done.

"It may not be a water-tight law, the bigger and better-connected companies can find a way around it," he said. "But it will help cut funding to some rebels, especially among smaller companies, and every little thing we can do to fight them helps."

Golooba-Mutebi said the United States would have to work with Congolese authorities for the law to be effective.

Human rights groups hope other nations will follow suit. Activists have campaigned against the so-called "conflict minerals" for years, and blame them for funding more than a decade of violence. The war and its aftermath, including hunger and diseases, have killed at least 5 million people and displaced scores. Rebels have used sexual violence as a weapon of war, and raped hundreds of thousands of women and girls.

"Funding for armed groups often comes from the sale of minerals -- often to American companies -- from mines the groups control," said Rep. Jim McDermott, a Democrat from Washington state. "This legislation will help save thousands of lives and help protect countless women in the Democratic Republic of Congo by cutting off a key source of funding for armed groups."

The law requires companies to use independent experts to certify whether their minerals are conflict-free.